Pen



FIG. 1 is a front, right side, top perspective view of the pen;

FIG. 2 is a front, right side, top perspective view of the pen shown in FIG. 1 in a configuration with the cap removed;

FIG. 3 is a right side elevational view of the pen shown in FIG. 1;

FIG. 4 is a top plan view of the pen shown in FIG. 1;

FIG. 5 is a front elevational view of the pen shown in FIG. 1; and,

FIG. 6 is a back elevational view of the pen shown in FIG. 1.

The structure in broken lines forms no part of the claimed design. 

The ornamental design for a pen, as shown and described. 